Things are starting to cook for Barry Levinson’s “Diner.” Sources say the musical, based on his 1982 autobiographical movie of the same title, had a “creative workshop” — with Levinson, composer Sheryl Crow and director Kathleen Marshall — just before the holidays, with “Book of Mormon” star Andrew Rannells reading the role of Fenwick, Annaleigh Ashford of off-Broadway’s “Rent” the part of Beth and “Anything Goes” star Colin Donnell reading Boogie. (The parts were played in the movie by Kevin Bacon, Ellen Barkin and Mickey Rourke.) Sources said the actors were “blown away” to have pop star Crow helping them with the tunes, which are inspired by the story, set in Baltimore of 1959. “The music is going to shock the hell out of people,” said a source. “It really delivers, and got a fantastic response.” “Diner” will be fully cast by spring, sources say, and then head directly into rehearsals before an out-of-town run in late July. The show will open in the fall.